Method, system and program product supporting phase events in a simulation model of a digital system

ABSTRACT

According to a method of simulation processing, an instrumented simulation executable model of a design is built by compiling one or more hardware description language (HDL) files specifying one or more design entities within the design and one or more instrumentation entities and instantiating instances of the one or more instrumentation entities within instances of the one or more design entities. Operation of the design is then simulated utilizing the instrumented simulation executable model. Simulating operation includes each of multiple instantiations of the one or more instrumentation entities generating a respective external phase signal representing an occurrence of a particular phase of operation and instrumentation combining logic generating from external phase signals of the multiple instantiations of the one or more instrumentation entities an aggregate phase signal representing an occurrence of the particular phase.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is also related to co-pending U.S. patent application Ser. No. 11/006,093, which is assigned to the assignee of the present invention and incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates in general to designing and simulating digital devices, modules and systems, and in particular, to a method and system for computer simulation of digital devices, modules and systems utilizing a hardware description language (HDL) model.

2. Description of the Related Art

Verifying the logical correctness of a digital design and debugging the design, if necessary, are very important steps in most digital design processes. Logic networks are tested either by actually building networks or by simulating networks on a computer. As logic networks become highly complex, it becomes necessary to simulate a design before the design is actually built. This is especially true when the design is implemented as an integrated circuit, since the fabrication of integrated circuits requires considerable time and correction of mistakes is quite costly. The goal of digital design simulation is the verification of the logical correctness of the design.

In a typical automated design process that is supported by a conventional electronic computer-aided design (ECAD) system, a designer enters a high-level description utilizing a hardware description language (HDL), such as VHDL, producing a representation of the various circuit blocks and their interconnections. The ECAD system compiles the design description into a format that is best suited for simulation. A simulator is then utilized to verify the logical correctness of the design prior to developing a circuit layout.

A simulator is typically a software tool that operates on a digital representation, or simulation model of a circuit, and a list of input stimuli (i.e., testcase) representing inputs of the digital system. A simulator generates a numerical representation of the response of the circuit, which may then either be viewed on the display screen as a list of values or further interpreted, often by a separate software program, and presented on the display screen in graphical form. The simulator may be run either on a general-purpose computer or on another piece of electronic apparatus, typically attached to a general purpose computer, specially designed for simulation. Simulators that run entirely in software on a general-purpose computer will hereinafter be referred to as “software simulators”. Simulators that are run with the assistance of specially designed electronic apparatus will hereinafter be referred to as “hardware simulators”.

Usually, software simulators perform a very large number of calculations and operate slowly from the user's point of view. In order to optimize performance, the format of the simulation model is designed for very efficient use by the simulator. Hardware simulators, by nature, require that the simulation model comprising the circuit description be communicated in a specially designed format. In either case, a translation from an HDL description to a simulation format, hereinafter referred to as a simulation executable model, is required.

The present invention appreciates that certain events, such as reaching the end of a particular simulation testcase, are difficult to detect in a conventional simulation executable model. For example, in conventional simulation environments, a designer may detect the occurrence of the end of a testcase by incorporating into the simulation executable model special-purpose, hand-built logic to monitor specific signals for which a particular set of values indicates that the end of a testcase has been reached. In some cases, the complexity of such monitoring logic may approach the complexity of the simulated circuit being monitored. Consequently, the present invention appreciates that it would be useful and desirable to provide a method, system and program product that improve the detection and visibility of certain events, such as end of testcase events, within simulation executable models.

SUMMARY OF THE INVENTION

According to a method of simulation processing, an instrumented simulation executable model of a design is built by compiling one or more hardware description language (HDL) files specifying one or more design entities within the design and one or more instrumentation entities and instantiating instances of the one or more instrumentation entities within instances of the one or more design entities. Operation of the design is then simulated utilizing the instrumented simulation executable model. Simulating operation includes each of multiple instantiations of the one or more instrumentation entities generating a respective external phase signal representing an occurrence of a particular phase of operation and instrumentation combining logic generating from external phase signals of the multiple instantiations of the one or more instrumentation entities an aggregate phase signal representing an occurrence of the particular phase.

All objects, features, and advantages of the present invention will become apparent in the following detailed written description.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a pictorial representation of a data processing system;

FIG. 2 depicts a representative hardware environment of the data processing system illustrated in FIG. 1;

FIG. 3A is a simplified block diagram illustrating a digital design entity that may be instrumented in accordance with the teachings of the present invention;

FIG. 3B is a diagrammatic representation depicting a simulation model that may be instrumented in accordance with the teachings of the present invention;

FIG. 3C is a flow diagram illustrating of a model build process that may be implemented in accordance with the teachings of the present invention;

FIG. 3D is a block diagram depicting data structures that may be instrumented in accordance with the teachings of the present invention;

FIG. 4A is a simplified block diagram representative of an instrumentation entity;

FIG. 4B is a simplified block diagram of a simulation model instrumented in accordance with the teachings of the present invention;

FIG. 4C illustrates exemplary sections of HDL syntax that maybe utilized in accordance with the teachings of the present invention;

FIG. 4D is a flow diagram depicting a model build process in accordance with the teachings of the present invention;

FIG. 4E is a block diagram representation of memory data structures constructed in accordance with the teachings of the present invention;

FIG. 5A is a logic diagram representation of a runtime disable mechanism in accordance with the teachings of the present invention;

FIG. 5B is a block diagram representation of functional units utilized to execute the method and system of the present invention on a hardware simulator in accordance with the teachings of the present invention;

FIG. 6 illustrates a conventional finite state machine that may be instrumented with an embedded checker in accordance with the teachings of the present invention;

FIG. 7 depicts a conventional finite state machine design entity;

FIG. 8 illustrates a hardware description language file including embedded instrumentation in accordance with the teachings of the present invention;

FIG. 9 depicts a hardware description language design entity included embedded instrumentation in accordance with the teachings of the present invention;

FIG. 10A is a block diagram illustrating a simulation model containing a number of design and instrumentation entities;

FIG. 10B depicts a data structure for declaring an event within a simulation model in accordance with one embodiment of the present invention;

FIG. 10C illustrates a list of extended event data structures for the simulation model in FIG. 10A;

FIG. 10D depicts a data structure for declaring an event within a simulation model in accordance with an alternate embodiment of the present invention;

FIG. 11A is a block diagram illustrating a simulation model in which the hierarchical event processing of the present invention is applicable;

FIG. 11B depicts a set of input port mapping comments for performing hierarchical processing of simulation model events in accordance with a first embodiment of the present invention;

FIG. 11C illustrates a set of input port mapping comments for performing hierarchical processing of simulation model events in accordance with a second embodiment of the present invention;

FIG. 12A depicts a representative target design entity with an instrumentation entity containing random instrumentation logic implemented in accordance with the teachings of the present invention;

FIG. 12B illustrates an exemplary HDL file for implementing instrumentation logic within an HDL design entity in accordance with the teachings of the present invention;

FIG. 13A depicts an exemplary design entity containing a multi-bit simulation signal;

FIG. 13B illustrates a design entity wherein signal injection is implemented in accordance with the teachings of the present invention;

FIG. 13C depicts an exemplary HDL source file that describes an instrumentation entity in accordance wit the teachings of the present invention; and

FIG. 14 is a block diagram depicting an eventlist file for count events during a simulation run of a simulation model.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The present invention provides for accurate and comprehensive monitoring of a digital circuit design in which a designer creates instrumentation modules utilizing the same hardware description language (HDL) as utilized for the design itself. HDLs, while suited to the needs of digital designers can also be effectively utilized for a number of checking functions. In accordance with the present invention, instrumentation modules are utilized to monitor specified design parameters while not becoming compiled as an integral part of the design itself. Furthermore, since the instrumentation modules are written in the same HDL as utilized in the actual design, such modules are platform and simulator independent. Unlike checking done with C or C++ programs, HDL instrumentation can be compiled and run directly without loss of performance on hardware simulators.

With reference now to the figures, and in particular with reference to FIG. 1, there is depicted a pictorial representation of a data processing system 10 with which the present invention may be advantageously utilized. As illustrated, data processing system 10 comprises a workstation 12 to which one or more nodes 13 are connected. Workstation 12 preferably comprises a high performance multiprocessor computer, such as one of the POWER line of computer systems available from International Business Machines (IBM) Corporation of Armonk, N.Y. Workstation 12 preferably includes nonvolatile and volatile internal storage for storing software applications comprising an ECAD system, which can be utilized to develop and verify a digital circuit design in accordance with the method and system of the present invention. As depicted, nodes 13 include a display device 14, a keyboard 16, and a mouse 20. The ECAD software applications executed within workstation 12 preferably display a graphic user interface (GUI) within display screen 22 of display device 14 with which a digital circuit designer can interact using a keyboard 16 and mouse 20. Thus, by entering appropriate inputs utilizing keyboard 16 and mouse 20, the digital circuit designer is able to develop and verify a digital circuit design according to the method described further hereinbelow.

FIG. 2 is a more detailed block diagram of data processing system 10. As illustrated, data processing system 10 includes one or more Central Processing Units (CPUs) 24, such as a conventional microprocessor, and a number of other components interconnected via system interconnect 26. Although not depicted in FIG. 2, CPUs such as CPU 24 typically include a control unit that organizes data and program storage in a computer memory and transfers the data and other information between the various parts of the computer system. CPUs also generally include one or more arithmetic logic units that execute arithmetical and logical operations, such as addition, comparison, multiplication and so forth.

Data processing system 10 further includes a random-access memory (RAM) 28, a read-only memory (ROM) 30, a display adapter 32 supporting connection of a display device 14, and an I/O adapter 34 for connecting peripheral devices (e.g., disk and tape drives 33). Data processing system 10 further includes a communications adapter 42 for connecting data processing system 10 to a communications network and a user interface adapter 36 for connecting keyboard 16, mouse 20, speaker 38, microphone 40, and/or other user interface devices to system interconnect 26.

As will be appreciated by those skilled in the art, data processing system 10 operates under the control of an operating system (e.g., AIX) and one or more other programs, which may reside in any suitable computer-readable media such as RAM 28, ROM 30, a magnetic disk, magnetic tape, or optical disk (the last three being located in disk and tape drives 33). These programs include a control program 46 that resides within main memory 44 and contains program code that, when processed by CPU 24, carries out the operations depicted in FIG. 4D and FIG. 4E described herein.

Simulated digital circuit design models are comprised of at least one and usually many sub-units referred to hereinafter as design entities. FIG. 3A is a block diagram representation of an exemplary design entity 300 in which the method and system of the present invention may be implemented. Design entity 300 is defined by a number of components: an entity name, entity ports, and a representation of the function performed by design entity 300. Each entity within a given model has a unique name (not explicitly shown in FIG. 3A) that is declared in the HDL description of each entity. Furthermore, each entity typically contains a number of signal interconnections, known as ports, to signals outside the entity. These outside signals may be primary input/outputs (I/Os) of an overall design or signals connecting to other entities within an overall design.

Typically, ports are categorized as belonging to one of three distinct types: input ports, output ports, and bi-directional ports. Design entity 300 is depicted in as having a number of input ports 303 that convey signals into design entity 300. Input ports 303 are connected to input signals 301. In addition, design entity 300 includes a number of output ports 306 that convey signals out of design entity 300. Output ports 306 are connected to a set of output signals 304. Bi-directional ports 305 are utilized to convey signals into and out of design entity 300. Bi-directional ports 305 are in turn connected to a set of bi-directional signals 309. An entity, such as design entity 300, need not contain ports of all three types, and in the degenerate case, contains no ports at all. To accomplish the connection of entity ports to external signals, a mapping technique, known as a “port map”, is utilized. A port map (not explicitly depicted in FIG. 3A) consists of a specified correspondence between entity port names and external signals to which the entity is connected. When building a simulation model, ECAD software is utilized to connect external signals to appropriate ports of the entity according to a port map specification.

Finally, design entity 300 contains a body section 308 that describes one or more functions performed by design entity 300. In the case of a digital design, body section 308 contains an interconnection of logic gates, storage elements, etc., in addition to instantiations of other entities. By instantiating an entity within another entity, a hierarchical description of an overall design is achieved. For example, a microprocessor may contain multiple instances of an identical functional unit. As such, the microprocessor itself will often be modeled as a single entity. Within the microprocessor entity, multiple instantiations of any duplicated functional entities will be present.

Referring now to FIG. 3B, there is illustrated a diagrammatic representation of an exemplary simulation model 329 that may be utilized in a preferred embodiment of the present invention. Simulation model 329 includes multiple hierarchical design entities. For visual simplicity and clarity, the ports and signals interconnecting the entities within simulation model 329 have not been explicitly shown. In any model, one and only one entity is the so-called “top-level entity”. A top-level entity 320 is that entity which encompasses all other entities within simulation model 329. That is to say, top-level entity 320 instantiates, either directly or indirectly, all descendant entities within a design. Simulation model 329 consists of top-level entity 320 which directly instantiates two instances, 321 a and 321 b, of an FXU entity 321 and a single instance of an FPU entity 322. Each instantiation has an associated description, which contains an entity name and a unique instantiation name. For top-level entity 320, description 310 is labeled “TOP:TOP”. Description 310 includes an entity name 312, labeled as the “TOP” preceding the colon, and also includes an instantiation name 314, labeled as the “TOP” following the colon.

It is possible for a particular entity to be instantiated multiple times as is depicted with instantiations 321 a and 321 b of FXU entity 321. Instantiations 321 a and 321 b are distinct instantiations of FXU entity 321 with instantiation names FXU0 and FXU1 respectively. Top-level entity 320 is at the highest level within the hierarchy of simulation model 329. An entity that instantiates a descendant entity will be referred to hereinafter as an “ancestor” of the descendant entity. Top-level entity 320 is therefore the ancestor that directly instantiates FXU entity instantiations 321 a and 321 b. At any given level of a simulation model hierarchy, the instantiation names of all instantiations must be unique.

In addition to FXU entity instantiations 321 a and 321 b, top-level entity 320 directly instantiates a single instance of a FPU entity 322 having an entity name FPU and instantiation name FPU0. Within an entity description, it is common for the entity name to match the instantiation name when only one instance of that particular entity is placed at a given level of a simulation model hierarchy. However, this is not required as shown by entity 322 (instantiation name FPU0, entity name FPU).

Within instantiation 321 a of FXU entity 321, single instance entities 325 a and 326 a of entity A 325 and entity B 326 respectively, are directly instantiated. Similarly, instantiation 321 b of the same FXU entity contains instantiations 325 b and 326 b of entity A 325 and entity B 326 respectively. In a similar manner, instantiation 326 a and instantiation 326 b each directly instantiate a single instance of entity C 327 as entities 327 a and 327 b respectively. The nesting of entities within other entities can continue to an arbitrary level of complexity provided that all entities instantiated, whether singly or multiply, have unique entity names and the instantiation names at any given level of the hierarchy are unique with respect to one another. Each entity is constructed from one or more HDL files that contain the information necessary to describe the entity.

Associated with each entity instantiation is a so called “instantiation identifier”. The instantiation identifier for a given instantiation is a string consisting of the enclosing entity instantiation names proceeding from the top-level entity instantiation name. For example, the instantiation identifier of instantiation 327 a of entity C 327 within instantiation 321 a of FXU entity 321 is “TOP.FXU0.B.C”. This identifier serves to uniquely identify each instantiation within a simulation model.

Referring now to FIG. 3C, there is depicted a flow diagram of a model build process which may be implemented in a preferred embodiment of the present invention. The process begins with one or more design entity HDL source code files 340 and, potentially, one or more design entity intermediate format files 345, hereinafter referred to as “proto files” 345, available from a previous run of an HDL compiler 342. HDL compiler 342 processes HDL file(s) 340 beginning with the top level entity of a simulation model and proceeding in a recursive fashion through all HDL or proto file(s) describing a complete simulation model. For each of HDL files 340 during the compilation process, HDL compiler 342, examines proto files 345 to determine if a previously compiled proto file is available and consistent. If such a file is available and consistent, HDL compiler 342 will not recompile that particular file, but will rather refer to an extant proto file. If no such proto file is available or the proto file is not consistent, HDL compiler 342 explicitly recompiles the HDL file 340 in question and creates a proto file 344, for use in subsequent compilations. Such a process will be referred to hereinafter as “incremental compilation” and can greatly speed the process of creating a simulation executable model 348. Incremental compilation is described in further detail hereinbelow. Once created by HDL compiler 342, proto files 344 are available to serve as proto files 345 in subsequent compilations.

In addition to proto files 344, HDL compiler 342 also creates two sets of data structures, design entity proto data structures 341 and design entity instance data structures 343, in memory 44 of computer system 10. Design entity proto data structures 341 and design entity instance data structures 343, serve as a memory image of the contents of a simulation executable model 348. Data structures 341 and 343 are passed, via memory 44, to a model build tool 346 that processes data structures 341 and 343 into simulation executable model 348.

It will be assumed hereinafter that each entity is described by a single HDL file. Depending on convention or the particular HDL in which the current invention is practiced, this restriction may be required. However, in certain circumstances or for certain HDLs it is possible to describe an entity by utilizing more than one HDL file. Those skilled in the art will appreciate and understand the extensions necessary to practice the present invention if entities are permitted to be described by multiple HDL files. Furthermore, it will be assumed that there is a direct correspondence, for each entity, between the entity name and both of the following: the name of the HDL file representing the entity, and the name of the proto file for the entity.

In the following description, an HDL source code file corresponding to a given entity will be referred to by an entity name followed by “.vhdl”. For example, the HDL source code file that describes top-level entity 320 will be referred to as TOP.vhdl. This labeling convention serves as a notational convenience only and should not be construed as limiting the applicability of the present invention to HDLs other than VHDL.

Returning to FIG. 3B, it can be seen that each entity may instantiate, either directly or indirectly, one or more other entities. For example, the FXU entity directly instantiates A entity 325 and B entity 326. Furthermore, B entity 326 directly instantiates C entity 327. Therefore, FXU entity 321 instantiates, directly or indirectly, A entity 325, B entity 326 and C entity 327. Those entities, that are directly or indirectly instantiated by another entity, will be referred to hereinafter as “descendants”. The descendants of top level entity 320 are FXU entity 321, FPU entity 322, A entity 325, B entity 326, and C entity 327. It can be seen that each entity has a unique set of descendants and that each time an entity is instantiated, a unique instance of the entity and its descendants is created. Within simulation model 329, FXU entity 321 is instantiated twice, FXU:FXU0 321 a and FXU:FXU1 321 b, by top-level entity 320. Each instantiation of FXU entity 321 creates a unique set of instances of the FXU, A, B, and C entities.

For each entity, it is possible to define what is referred to as a “bill-of-materials” or BOM. A BOM is a list of HDL files having date and time stamps of the entity itself and the entity's descendants. Referring again to FIG. 3C, the BOM for an entity is stored in proto file 344 after compilation of the entity. Therefore, when HDL compiler 342 compiles a particular HDL source code file among HDL files 340, a proto file 344 is generated that includes a BOM listing the HDL files 340 that constitute the entity and the entity's descendants, if any. The BOM also contains the date and time stamp for each of the HDL files referenced as each appeared on disk/tape 33 of computer system 10 when the HDL file was being compiled.

If any of the HDL files constituting an entity or the entity's descendants is subsequently changed, proto file 344 will be flagged as inconsistent and HDL compiler 342 will recompile HDL file 340 on a subsequent re-compilation as will be described in further detail below. For example, going back to FIG. 3B, the HDL files referenced by the BOM of FXU entity 321 are FXU.vhdl, A.vhdl, B.vhdl and C.vhdl, each with appropriate date and time stamps. The files referenced by the BOM of top-level entity 320 are TOP.vhdl, FXU.vhdl, A.vhdl, B.vhdl, C.vhdl, and FPU.vhdl with appropriate date and time stamps.

Returning to FIG. 3C, HDL compiler 342 creates an image of the structure of a simulation model in main memory 44 of computer system 10. This memory image is comprised of the following components: “proto” data structures 341 and “instance” data structures 343. A proto is a data structure that, for each entity in the model, contains information about the ports of the entity, the body contents of the entity, and a list of references to other entities directly instantiated by the entity (in what follows, the term “proto” will be utilized to refer to the in-memory data structure described above and the term “proto file” will be utilized to describe intermediate format file(s) 344). Proto files 344 are therefore on-disk representations of the in-memory proto data structure produced by HDL compiler 342.

An instance data structure is a data structure that, for each instance of an entity within a model, contains the instance name for the instance, the name of the entity the instance refers to, and the port map information necessary to interconnect the entity with external signals. During compilation, each entity will have only one proto data structure, while, in the case of multiple instantiations of an entity, each entity may have one or more instance data structures.

In order to incrementally compile a model efficiently, HDL compiler 342 follows a recursive method of compilation in which successive entities of the model are considered and loaded from proto files 345 if such files are available and are consistent with the HDL source files constituting those entities and their descendants. For each entity that cannot be loaded from existing proto files 345, HDL compiler 342 recursively examines the descendants of the entity, loads those descendant entities available from proto file(s) 345 and creates, as needed, proto files 344 for those descendants that are inconsistent with proto files 345. Pseudocode for the main control loop of HDL compiler 342 is shown below (the line numbers to the right of the pseudocode are not a part of the pseudocode, but merely serve as a notational convenience).

process_HDL_file(file) 5 { 10 if (NOT proto_loaded(file)) { 15 if (exists_proto_file(file) AND check_bom(file)) { 20 load_proto(file); 25 } else { 30 parse_HDL_file(file) 35 for (all instances in file) { 40 process_HDL_file(instance); 45 } 50 create_proto(file); 55 write_proto_file(file); 60 } 65 } 70 create_instance(file): 75 } 80

When compiler 342 is initially invoked, no proto data structures 341 or instance data structures 343 are present in memory 44 of computer system 10. The main control loop, routine process_HDL_file( ) (line 5), is invoked and passed the name of the top level entity by means of parameter “file”. The algorithm first determines if a proto data structure for the current entity is present in memory 44 by means of routine proto_loaded( ) (line 15). Note that the proto data structure for the top level entity will never be present in memory because the process starts without any proto data structures loaded into memory 44. If a matching proto data structure is present in memory 44, instance data structures for the current entity and the current entity's descendants, if any, are created as necessary in memory 44 by routine create_instance( ) (line 75).

However, if a matching proto data structure is not present in memory 44, control passes to line 20 where routine exists_proto_file( ) examines proto files 345 to determine if a proto file exists for the entity. If and only if a matching proto file exists, routine check_bom( ) is called to determine whether proto file 345 is consistent. In order to determine whether the proto file is consistent, the BOM for the proto file is examined. Routine check_bom( ) examines each HDL source code file listed in the BOM to determine if the date or time stamps for the HDL source code file have changed or if the HDL source code file has been deleted. If either condition occurs for any file in the BOM, the proto file is inconsistent and routine check_bom( ) fails. However, if check_bom( ) is successful, control is passed to line 25 where routine load_proto( ) loads the proto file and any descendant proto files into memory 44, thus creating proto data structures 341 for the current entity and the current entity's descendants, if any. The construction of process_HDL_file( ) ensures that once a proto file has been verified as consistent, all of its descendant proto files, if any, are also consistent.

If the proto file is either non-existent or is not consistent, control passes to line 35 where routine parse_HDL_file( ) loads the HDL source code file for the current entity. Routine parse_HDL_file( ) (line 35) examines the HDL source code file for syntactic correctness and determines which descendant entities, if any, are instantiated by the current entity. Lines 40, 45, and 50 constitute a loop in which the routine process_HDL_file( ) is recursively called to process the descendent entities that are called by the current entity. This process repeats recursively traversing all the descendants of the current entity in a depth-first fashion creating proto data structures 341 and proto data files 344 of all descendants of the current entity. Once the descendant entities are processed, control passes to line 55 where a new proto data structure is created for the current entity in memory 44 by routine create_proto( ). Control then passes to line 60 where a new proto file 344, including an associated BOM, is written to disk 33 by routine write proto_file( ). Finally, control passes to line 75 where routine create_instance( ) creates instance data structures 343 for the current entity and any descendant entities as necessary. In this manner, process_HDL_file( ) (line 5) recursively processes the entire simulation model creating an in-memory image of the model consisting of proto data structures 341 and instance data structures 343.

With reference now to FIG. 3D there is depicted a block diagram representing compiled data structures, which may be implemented in a preferred embodiment of the present invention. Memory 44 contains proto data structures 361, one for each of the entities referred to in simulation model 329. In addition, instantiations in simulation model 329 are represented by instance data structures 362. Instance data structures 362 are connected by means of pointers indicating the hierarchical nature of the instantiations of the entities within simulation model 329. Model build tool 346 in FIG. 3C processes the contents of memory 44 into memory data structures in order to produce simulation executable model 348.

In order to instrument simulation models, the present invention makes use of entities known as “instrumentation entities,” which are in contrast to the entities constituting a design which are referred to herein as “design entities”. As with design entities, instrumentation entities are described by one or more HDL source code files and consist of a number of signal ports, a body section, and an entity name. In what follows, it will be assumed that an instrumentation entity is described by a single HDL file. Those skilled in the art will appreciate and understand extensions necessary to practice the current invention for an instrumentation entity that is described by multiple HDL files. Each instrumentation entity is associated with a specific design entity referred to hereinafter as the “target entity”.

With reference now to FIG. 4A, there is illustrated a block diagram representation of an instrumentation entity 409. Instrumentation entity 409 includes a number of input ports 400 that are connected to signals 401 within a target entity (not depicted in FIG. 4A). A body section 402 contains logic necessary to detect occurrences of specified conditions within the target entity and generate simulation model “events” with respect to signals 401. Four distinct types of events may be generated: “count” events, “fail” events, “harvest” events, and “phase” events, each described below in turn. Body section 402 contains internal logic for detecting occurrences of conditions precipitating generation of these events. A set of multi-bit output ports 403, 404, 405 and 430 are connected to external instrumentation logic (depicted in FIG. 4B) by external signals 406, 407, 408 and 432, respectively. Output ports 403, 404, 405 and 430 thus provide the connection from the internal logic in body section 402 to the external instrumentation logic which is utilized to indicate the occurrence of count, fail, harvest, and phase events.

A fail or failure event is a sequence of signal values that indicate a failure in the correct operation of the simulation model. Each instrumentation entity monitors the target entity for any desired number of failure events. Each occurrence of a failure event is assigned to a particular signal bit on output port 403. Logic within body section 402 produces an active high pulse on a specified bit of signal 403 when a failure condition is detected. Such activation of signal 403 is defined as a failure event. This error indication is conveyed by external signal 406 to external instrumentation logic (depicted in FIG. 4B as external instrumentation logic block 420), which flags the occurrence of the failure event.

A count event is a sequence of signal values that indicate the occurrence of an event within a simulation model for which it would be advantageous to maintain a count. Count events are utilized to monitor the frequency of occurrence of specific sequences within a simulation model. Each instrumentation entity can monitor the target entity for any desired number of count events. Each count event is assigned to a particular signal bit on output port 405. Logic block 402 contains the logic necessary to detect the occurrence of the desired count events and produces an active high pulse on the specified bit of signal 405 when a count event is detected. This count indication is conveyed by external signal 408 to instrumentation logic, which contains counters utilized to record the number of occurrences of each count event.

The third event type, a harvest event, is a sequence of signal values that indicate the occurrence of a specific operative circumstance, which would be advantageous to be able to reproduce. When a harvest event occurs, a register within an external instrumentation logic block is loaded to indicate at what point within a simulation run the event occurred, and a flag is set to indicate the occurrence of the specific circumstance. The details of the simulation run can thus be saved in order to recreate the specific circumstance monitored by the harvest event. Logic block 402 contains the logic necessary to detect the harvest events.

Each instrumentation entity can detect any desired number of harvest events that are each assigned to a particular signal bit on output port 404. Logic within block 402 produces an active high pulse on the specified bit of signal 404 when a harvest event is detected. This harvest event detection is conveyed by external signal 407 to external instrumentation logic that contains a register and flag for each harvest event. The register is utilized to record at which point in the simulation run the harvest event occurred, and the flag is utilized to indicate the occurrence.

A phase event is an indication that one or more signal states defining a specified phase of operation of the simulation model are present in a target design entity. Each instrumentation entity monitors the target design entity for any desired number of phase events. Each occurrence of a phase event is assigned to a particular signal bit on output port 430. Logic within body section 402 produces an active high pulse on a specified bit of signal 430 when the signal state(s) signifying the phase event are detected within the target design entity. Such activation of signal 430 is defined as a phase event. This phase indication is conveyed by external signal 432 to external instrumentation logic (depicted in FIG. 4B as external instrumentation logic block 420), which flags the occurrence of the phase event.

With reference now to FIG. 4B, there is depicted a block diagram representation of simulation model 329 instrumented in accordance with the teachings of the present invention. As can be seen in FIG. 4B, instances 410 and 411 of an instrumentation entity FXUCHK are utilized to monitor instances 321 a and 321 b of an FXU entity. For each FXU instantiations of 321 a and 321 b, an FXUCHK instantiation, 410 and 411 respectively, is automatically generated by the mechanism of the present invention. In a similar fashion, instrumentation entity FPUCHK 412 is instantiated to monitor FPU entity 322.

As depicted in FIG. 4B, entity FXUCHK monitors signals Q 372, R 376, and S 374 within each of instances 321 a and 321 b of the FXU entity. Signal Q 372 is a signal within the instances 325 a and 325 b of descendant entity A. Likewise, signal S 374 is a signal within descendant entity C that resides within descendant entity B. Finally, signal R 376 occurs directly within FXU entity 321. Although an instrumentation entity may monitor any signal within a target entity or the target entity's descendent entities, signals outside the target entity cannot be monitored.

Based upon the monitored signals within the target design entity instantiation, each instrumentation entity generates a respective set of external signals 415, 416, 417. The fail, count, harvest and phase signals within external signals 415, 416 and 417 are connected to an instrumentation logic block 420 containing logic for recording occurrences of each of the fail, count and harvest event types. For the count events monitored in simulation model 329, a set of counters 421 is utilized to count the number of occurrences of each count event. In a similar manner, a set of flags 424 is utilized to record the occurrence of failure events. Also, a set of counters 422 and flags 423 are combined and utilized to record the point at which a harvest event occurs and its occurrence, respectively. In one embodiment of the present invention, a cycle number is captured and stored utilizing counters 422 and flags 423 to record a harvest event.

As depicted, instrumentation logic block 420 also contains combining logic 427 a-427 n for generating from the phase signals within external signals 415, 416 and 417 what is referred to herein as “aggregate phase events.” That is, each instance of combining logic 427 logically combines the individual phase events of a particular aggregate phasename and generates a respective aggregate phase event signal 429 that has a state indicating either the presence or absence in a current simulation cycle of the criteria defining a phase of operation across a region of simulation executable model 329.

To facilitate instantiation and connection of instrumentation entities, instrumentation entity HDL source code files include a specialized comment section, hereinafter referred to as “instrumentation entity description”, that indicates the target entity, the signals within the target entity to be monitored, and information specifying types of events to be monitored.

With reference now to FIG. 4C, there is illustrated an exemplary HDL file 440 that describes instrumentation entity FXUCHK depicted in FIG. 4B. HDL file 440 utilizes the syntax of the VHDL hardware description language. In the VHDL language, lines beginning with two dashes (“--”) are recognized by a compiler as being comments. The method and system of the present invention utilize comments of a non-conventional form to indicate information about an instrumentation entity. FIG. 4C depicts one embodiment of the present invention in which comments begin with two exclamation points in order to distinguish these comments from conventional comments in instrumentation HDL file 440. It will be appreciated by those skilled in the art that the exemplary syntax utilized in FIG. 4C for the provision of unconventional comments is but one of many possible formats.

Within HDL file 440, the I/O ports of a FXUCHK entity are declared in entity declaration 450. Within entity declaration 450, three input ports, S_IN , Q_IN , and R_IN, respectively, are declared. Input ports, S_IN, Q_IN, and R_IN, will be attached to signal S, 374, signal Q, 372, and signal R, 376 respectively as described below. Input port, CLOCK, is also declared and will be connected to a signal, CLOCK, within the FXU entity. In addition, four output ports are declared: fails (0 to 1), counts (0 to 2), harvests (0 to 1) and phases (0 to 0). These output ports provide failure, count, harvest and phase signals for two failure events, three count events, two harvest events and one phase event. The names of the output ports are fixed by convention in order to provide an efficient means for automatically connecting these signals to instrumentation logic block 420.

A set of instrumentation entity descriptors 451 is utilized to provide information about the instrumentation entity. As illustrated in FIG. 4C, descriptor comments 451 may be categorized in a number of distinct sections: prologue and entity name declaration 452, an input port map 453, a set of failure message declarations 454, a set of counter declarations 455, a set of harvest declarations 456, a set of phase declarations 490 and an epilogue 457.

The prologue and entity name 452 serve to indicate the name of the particular target entity that the instrumentation entity will monitor. Prologue and entity name declaration 452 also serves as an indication that the instrumentation entity description has begun. Specifically, the comment “--!! Begin” within prologue and entity name 452, indicates that the description of an instrumentation entity has begun. The comment “--!! Design Entity: FXU” identifies the target entity which, in HDL file 440, is design entity FXU. This declaration serves to bind the instrumentation entity to the target entity.

Input port map 453 serves as a connection between the input ports of an instrumentation entity and the signals to be monitored within the target entity. The comments begin with comment “--!! Inputs” and end with comment “--!! End Inputs”. Between these comments, comments of the form “--!! inst_ent_port_name=>trgt_ent_signal_name” are utilized, one for each input port of the instrumentation entity, to indicate connections between the instrumentation entity ports and the target entity signals. The inst_ent_port_name is the name of the instrumentation entity port to be connected to the target entity signal. The trgt_ent_signal_name is the name of the signal within the target entity that will be connected to the instrumentation entity port.

In some cases a signal to be monitored lies within a descendant of a target entity. This is the case for signal S 374, which is embedded within entity C which is a descendant of entity B 326 and target FXU entity 321. Input port map 453 includes an identification string for signal S 374, which consists of the instance names of the entities within the target entity each separated by periods (“.”). This identification string is pre-pended to the signal name. The signal mapping comment within input port map 453 for signal S 374 is therefore as follows: --!!S_IN=>B.C.S;

This syntax allows an instrumentation entity to connect to any signal within the target entity or the target entity's descendant entities. A signal appearing on the top level of the target design entity, has no pre-pended entity names; and therefore, has the following signal mapping comment: --!!R_IN=>R;

For signals on the top level of the target entity, a special connection method is provided. If the signal to be connected to has the same name as its corresponding signal in the port map of the instrumentation entity, no input port mapping comment is required and the signal will be automatically connected if no such comment is present. In other words, if the input port mapping comment is of the form: --!!signal=>signal; where signal is a legal signal name without periods (“.”), then the input port mapping comment is not required, and the system of the present invention will automatically make the connection. It is also possible to provide comments of the form given above to explicitly denote the signal connection. This mechanism is only operative for signals on the top level of the target entity.

Failure message declarations 454 begin with a comment of the form “--!! Fail Outputs;”, and end with a comment of the form “--!! End Fail Outputs;”. Each failure event output is associated with a unique event name and a failure message. This message may be output by the simulation run-time environment upon detecting a failure event. The unique failure event name is utilized to identify the specific failure event within the model. Each failure event signal may be declared by a comment of the form “--!! n: <eventname>“failure message”;” where n is an integer denoting the failure event to which the message is associated, <eventname> is the unique failure event name, and “failure message” is the message associated with the particular failure event. One and only one failure message declaration comment must be provided for each failure event monitored by the instrumentation entity.

Counter declaration comments 455 begin with a comment of the form “--!! Count Outputs;” and end with a comment of the form “--!! End Count Outputs;”. Each count event output is associated with a unique variable name. This name is associated with a counter in counter logic 421 FIG. 4B. The variable name provides a means to identify and reference the particular counter associated with a particular count event. Thus, a comment of the form “--!! n: <varname> qualifying_signal [+/−];” is associated with each counter event output. Within this convention, n is an integer denoting which counter event in the instrumentation module is to be associated with a variable name “varname,” and qualifying_signal is the name of a signal within a target design entity utilized to determine when to sample the count event pulse, as will be further described hereinbelow. The parameter “qualifying_signal” is followed by A+/−A to specify whether the qualifying signal will be a high active qualifying signal or a low active qualifying signal.

Harvest declarations 456 begin with a prologue comment of the form “--!! Harvest Outputs;” and end with a comment of the form “--!! End Harvest Outputs;”. Each harvest event output is associated with a unique event name and a message that may be output by the simulation runtime environment when a harvest event has occurred during a simulation run. Each harvest event signal is declared in the form “--!! n: <eventname>“harvest message”;” where n is an integer denoting which harvest event the message is to be associated with, <eventname> is the unique harvest event name and “harvest message” is the message to be associated with the particular harvest event. One, and only one, harvest message declaration comment must be provided for each harvest event monitored by the instrumentation entity.

Phase message declarations 490 begin with a comment of the form “--!! Phase Outputs;”, and end with a comment of the form “--!! End Phase Outputs;”. Each phase event output is associated with a unique event name and an aggregate phase name that tags the phase event as an input of a particular instance of combining logic 427 associated with that aggregate phase name. The unique phase event name is utilized to identify the specific aggregate phase event within the model. Each phase event signal may be declared by a comment of the form “--!! n: <eventname><phasename>;” where n is an integer denoting the bit in external signal 432 with which the phase event is associated, <eventname> is the unique phase event name, and <phasename> is the aggregate phase name with which the particular phase event is associated.

Harvest messages and event names, fail messages and event names, counter variable names, and phase event names for a simulation model are included in a simulation executable model, and lists of all the events within the model are produced in separate files at model build time. In this manner, each simulation model includes the information for each event monitored and a separate file containing this information for each event is available. Furthermore, as will be described below, the model build process names each event within the model (count, fail, harvest and phase) in such a manner as to insure that each event has a unique name with certain useful properties.

Finally, epilogue comment 457 consists of a single comment of the form “--!! End;”, indicating the end of descriptor comments 451. The remainder of instrumentation entity HDL file 440 that follows the I/O declarations described above is an entity body section 458. In entity body section 458, conventional HDL syntax is utilized to define internal instrumentation logic necessary to detect the various events on the input port signals and convey these events to the output port signals.

In addition to descriptor comments 451, that are located in the HDL source code file for an instrumentation entity, an additional comment line is required in the target entity HDL file. A comment of the form “--!! Instrumentation: name.vhdl”, where name.vhdl is the name of the instrumentation entity HDL file, is added to the target entity HDL source code file. This comment provides a linkage between the instrumentation entity and its target entity. It is possible to have more than one such comment in a target entity when more than one instrumentation entity is associated with the target entity. These HDL file comments will hereinafter be referred to as “instrumentation entity instantiations”.

With reference now to FIG. 4D, there is depicted a model build process implemented by program code in accordance with the teachings of the present invention. For ease of implementation, the program code that performs the illustrated model build process is depicted as including HDL compiler 462, an instrumentation load tool 464, and a model build tool 446, referred to herein collectively as “model build program code”. As noted above, processing of the model build program code may be advantageously controlled by a control program 46. In the model build process, instrumentation load tool 464 is utilized to alter the in-memory proto and instance data structures of a simulation model, thereby adding instrumentation entities to the simulation model. Instrumentation load tool 464 utilizes descriptor comments 451 within instrumentation HDL files 461 to create instance data structures for the instrumentation entities within a simulation model.

The model build process of FIG. 4D begins with design entity HDL files 340 and, potentially, one or more design entity proto files 345 (available from a previous run of HDL compiler 462), instrumentation entity HDL files 460, and potentially, one or more instrumentation entity proto files 461 (available from a previous run of HDL compiler 462) and an optional phase file 492.

In one preferred embodiment, phase file 492 lists the legal aggregate phasenames for the simulation model and, for each named phase, the Boolean operator (e.g., AND, OR, etc.) of the combining logic 427 that combines the phase event(s), if any, of that phase from each instrumentation entity to obtain an aggregate phase event signal 429. Thus, an entry within phase file 492 may take the form: <phasename>, <combining function>. It is also preferred if a special “end-of-testcase” (EOT) phasename is predefined, such that detection of a model-wide EOT phase can be utilized to halt execution of a testcase on a hardware accelerator, as discussed further below with respect to FIG. 5B.

Although not required, it is also preferable if each entry within phase file 492 also supports the definition of an associated region of the simulation model in which the specified phase name is valid. In this embodiment, an exemplary entry within phase file 492 may take the form: <phasename>, <combining function>, <instance>, where <instance> is an optional parameter specifying the design entity instance defining the region of the simulation model in which the specified aggregate phasename is valid. HDL compiler 462 is also preferably configured to interpret entries in phase file 492 having no specified <instance> parameter as being associated with the top-level design entity instance of the simulation model. Associating aggregate phasenames with particular regions of the simulation model in this manner permits HDL files from different projects to be synthesized into a single simulation model without concern for conflicting aggregate phasenames.

In a preferred embodiment, the predefined EOT phasename is not subject to regional definition, ensuring that the EOT phasename has the same name across all subsets of a simulation executable model and that no phasename conflict will arise for the EOT phasename when multiple smaller simulation models are combined to form a simulation executable model of a larger system. Because the EOT phasename is predefined, it is also unnecessary and preferably an error to explicitly enumerate the EOT phasename in a phase file 492.

HDL compiler 462 processes design entity HDL files 340 and instrumentation entity HDL files 460 following an augmentation of algorithm process_HDL_file( ) that provides for efficient incremental compilation of the design and instrumentation entities comprising a simulation model. HDL compiler 462 loads proto data structures from design entity proto files 345 and instrumentation entity protos files 460, if such proto files are available and consistent. If such proto files are not available or are not consistent, HDL compiler 462 compiles design entity HDL files 340 and instrumentation entity HDL files 460 in order to produce design entity proto files 344 and instrumentation entity proto files 468. (Design entity proto files 344 and instrumentation entity proto files 468 are available to serve as design entity proto files 345 and instrumentation entity proto files 460 respectively for a subsequent run of HDL compiler 462.)

HDL compiler 462 processes instrumentation entity HDL files 461, instrumentation entity proto files 460, design entity HDL files 340 and design entity proto files 345 by reference to phase file 492. In particular, HDL compiler 462 verifies that any <instance> parameter of an entry within phase file 492 has a corresponding design entity instance within design entity HDL files 340 or design entity proto files 345 and generates an error otherwise. In addition, HDL compiler 462 verifies that any aggregate phasename referenced within instrumentation entity HDL files 461 or instrumentation entity proto files 460 has a corresponding <phasename> parameter within an entry in phase file 492 and generates an error otherwise. No error is generated by HDL compiler 462 if aggregate phasenames specified within phase file 492 are unused within instrumentation entity HDL files 461 or instrumentation entity proto files 460.

In addition, HDL compiler 462 creates in-memory design proto data structures 463 and design instance data structures 465 for the design entities of a simulation model. HDL compiler 462 also creates in-memory instrumentation proto data structures 466 for the instrumentation entities of a simulation model.

In order to minimize processing overhead HDL compiler 462 neither reads nor processes descriptor comments 451. However, HDL compiler 462 does recognize instrumentation entity instantiation comments within target entity HDL files. As such, HDL compiler 462 cannot create instance data structures instrumentation entity data structures 467. The creation of instance data structures requires interconnection information contained within descriptor comments 451 not processed by HDL compiler 462. HDL compiler 462 does, however, create instrumentation proto data structures 466.

The in-memory design proto data structures 463, design instance data structures 465, and instrumentation entity proto data structures 466, are processed by instrumentation load tool 464. Instrumentation load tool 464 examines design entity proto data structures 463 and design entity instance data structures 465 to determine those design entities that are target entities. This examination is accomplished by utilizing a particular comment format as previously described.

All target entities that are loaded from design entity proto files 345 contain an instantiation for any associated instrumentation entity. Therefore, instrumentation load tool 464 merely creates an instance data structure 467 for any such instrumentation entity and passes, the unaltered design proto data structure 463 to instrumented design proto data structure 463 a, and passes design instance data structure 465 to instrumented design instance data structure 465 a.

If however, a target entity is loaded from design entity HDL files 340, rather than from design entity proto files 345, instrumentation load tool 464 must alter its design proto data structure 463 and its design instance data structure 465 to instantiate an associated instrumentation entity. An instrumented design proto data structure 463 a and instrumented design instance data structure 465 a are thereby produced. In addition, instrumentation load tool 464 creates an instrumentation instance data structure 467 for each instrumentation entity associated with the current design entity.

The design entity proto data structures 463 that are altered by instrumentation load tool 464 are saved to disk 33 of computer system 10 as design entity proto files 344. Design entity proto files 344, which may include references to instrumentation entities, are directly loaded by a subsequent compilation of a simulation model, thus saving processing by instrumentation load tool 464 on subsequent recompilations unless an alteration is made to a design entity or an associated instrumentation entity.

In order for HDL compiler 462 to determine if alterations were made to either a target design entity or the target design entity's associated instrumentation entities, the BOM of a target design entity is expanded to include the HDL files constituting the instrumentation entities. In this manner, HDL compiler 462 can determine, by inspection of the BOM for a given design entity, whether to recompile the design entity and the design entity's associated instrumentation entities or load these structures from proto files 345 and 461.

Instrumentation load tool 464 creates a unique proto and instance data structure for instrumentation logic block 420 and connects the fail, harvest, count and phase event signals from each instrumentation entity instantiation to instrumentation logic block 420. Model build tool 446 processes in-memory proto and instance data structures 463 a, 465 a, 467, 466 to produce instrumented simulation executable model 480.

In HDL compiler 462, algorithm process_HDL_file( ) is augmented to allow for the incremental compilation of design and instrumentation entities. A pseudocode implementation of a main control loop of HDL compiler 462 is shown below:

process_HDL_file2(file,design_flag) 5 { 10 if (NOT proto_loaded(file)) { 15 if (exists_proto_file(file) AND check_bom(file)) { 20 load_proto(file); 25 }else { 30 parse_HDL_file(file) 35 for (all instances in file) { 40 process_HDL_file2(instance, design_flag); 45 } 50 if (design_flag=TRUE) { 55 for (all instrumentation instances in file){ 60 process_HDL_file2(instance, FALSE); 65 } 70 } 75 create_proto(file); 80 write_proto_file(file); 90 } 95 } 100 if (design_flag=TRUE) { 105 create_instance(file); 110 } 115 } 120

Algorithm process_HDL_file2( ) is an augmentation to process_HDL_file( ) of HDL compiler 342 in order to support the creation of instrumented simulation models. The algorithm is invoked with the name of the top level design entity passed through parameter file and a flag indicating whether the entity being processed is a design entity or an instrumentation entity passed through parameter design_flag (design_flag=TRUE for design entities and FALSE for instrumentation entities). Algorithm process_HDL_file2( ) (line 5) first checks, by means of routine proto_loaded( ) (line 15), if the proto for the current entity is already present in memory 44. If so, processing passes to line 105. Otherwise, control is passed to line 20 and 25 where disk 33 of computer system 10 is examined to determine if proto files for the entity and its descendants (including instrumentation entities, if any) exist and are consistent. If so, the appropriate proto files are loaded from disk 10 by routine load_proto( ) (line 25) creating proto data structures, as necessary, in memory 44 for the current entity and the current entity's descendants including instrumentation entities.

If the proto file is unavailable or inconsistent, control passes to line 35 where the current entity HDL file is parsed. For any entities instantiated within the current entity, lines 40 to 55 recursively call process_HDL_file2( ) (line 5) in order to process these descendants of the current entity. Control then passes to line 55 where the design_flag parameter is examined to determine if the current entity being processed is a design entity or an instrumentation entity. If the current entity is an instrumentation entity, control passes to line 80. Otherwise, the current entity is a design entity and lines 60 to 70 recursively call process_HDL_file2( ) (line 5) to process any instrumentation entities instantiated by means of instrumentation instantiation comments. It should be noted that algorithm process_HDL_file2( ) (line 5) does not allow for instrumentation entities to monitor instrumentation entities. Any instrumentation entity instantiation comments within an instrumentation entity are ignored. Control then passes to line 80 where proto data structures are created in memory 44 as needed for the current entity and any instrumentation entities. Control then passes to line 90 where the newly created proto data structures are written, as needed to disk 33 of computer system 10.

Control finally passes to line 105 and 110 where, if the current entity is a design entity, instance data structures are created as needed for the current entity and the current entity's descendants. If the current entity is an instrumentation entity, routine create_instance( ) (line 110) is not called. Instrumentation load tool 464 is utilized to create the in-memory instance data structures for instrumentation entities.

It will be apparent to those skilled in the art that HDL compiler 462 provides for an efficient incremental compilation of design and instrumentation entities. It should also be noted that the above description is but one of many possible means for accomplishing an incremental compilation of instrumentation entities. In particular, although many other options also exist, much, if not all, of the functionality of instrumentation load tool 464 can be merged into HDL compiler 462.

With reference now to FIG. 4E wherein is shown a depiction of memory 44 at the completion of compilation of simulation model 329 with instrumentation entities FXUCHK and FPUCHK. Memory 44 contains proto data structures 481, one for each of the design and instrumentation entities referred to in simulation model 329. In addition, design and instrumentation instances in simulation model 329 are represented by instance data structures 482. The instance data structures are connected by means of pointers indicating the hierarchical nature of the instantiations of the design and instrumentation entities within simulation model 329.

With reference now to FIG. 5A, failure flags 424 of instrumentation logic block 420 are depicted in greater detail. Failure flags 424 comprise registers 500 a-500 n utilized to accept and store an indication of the occurrence of a failure event. In what follows, the operation of a single failure flag for a particular failure event 502 will be discussed. The operation of all failure flags is similar.

Register 500 a holds a value that represents whether a failure event 502 has occurred or not. Register 500 a is initially set to a value of ‘0’ by the simulation run-time environment at the beginning of a simulation run. When failure event 502, if enabled at register 507 a, occurs, register 500 a is set to a value of a logical ‘1’, thereby indicating the occurrence of a failure event. Register 500 a is driven by logical OR gate 501. Logical OR gate 501 performs a logical OR of the output of register 500 a and a qualified failure signal 503 to create the next cycle value for register 500 a. In this manner, once register 500 a is set to a logical ‘1’ by the occurrence of an enabled failure event, register 500 a maintains the value of a logical ‘1’ until reset by the simulation runtime environment. Likewise, register 500 a maintains a value of ‘0’ from the beginning of the simulation run until the occurrence of the failure event, if enabled.

Qualified failure signal 503 is driven by logical AND gate 505. Logical AND gate 505 produces, on qualified failure signal 503, the logical AND of failure signal 506 and the logical NOT of register 507 a. Register 507 a serves as an enabling control for qualified failure signal 503. If register 507 a contains a value of ‘0’, logical AND gate 505 will pass failure event signal 506 unaltered to qualified failure signal 503. In this manner, the monitoring of the failure event is enabled. Registers 507 a-507 n are set, by default, to a value of ‘0’. However, if register 507 a contains a value of a logical ‘1’, qualified failure signal 503 will remain at a value of ‘0’ irrespective of the value of failure event signal 506, thereby disabling the monitoring of failure event 502. In this manner, register 508, consisting of registers 507 a-507 n, can mask the occurrence of any subset of failure events in the overall simulation model from registers 500 a-500 n.

To efficiently implement the ability to selectively disable the monitoring of failure events, the simulation run-time environment includes a function that allows a user to disable monitoring of a specific failure event for a given instrumentation entity. This function will automatically set the appropriate registers among registers 507 a-507 n within register 508 to disable the monitoring of a particular failure event for every instance of the instrumentation entity within the overall simulation model. Instrumentation load tool 464 and model build tool 446 encode sufficient information within instrumented simulation executable model 480 to determine which failure bits within register 508 correspond to which instrumentation entities.

The ability to selectively disable monitoring of failure events is of particular use in large batch-simulation environments. Typically, in such an environment, a large number of general purpose computers, running software or hardware simulators, are dedicated to automatically running a large number of simulation runs. If a simulation model with a faulty instrumentation entity that incorrectly indicates failure events is run in such an environment, a large number of erroneous failures will be generated causing lost time. By selectively disabling failure events within instrumentation entities, the present invention allows simulation to continue while only disabling erroneous failure signals rather than having to disable all failure monitoring. This option is particularly useful when the process of correcting a faulty instrumentation entity and creating a new simulation model is substantially time consuming. The present invention also provides similar enabling and disabling structures for the harvest and count events within a model.

Logical OR gate 512 is utilized to produce a signal 511, which indicates whether any failure event within the model has occurred. This signal is utilized to allow hardware simulators to efficiently simulate simulation models that have been instrumented according to the teachings of the present invention.

It will further be appreciated upon reference to FIG. 5A that the illustrated technique for disabling particular failure events can also be applied to disable other types of events, such as phase events.

With reference now to FIG. 5B there is illustrated in greater detail, features of the present invention utilized to support efficient execution of an instrumented simulation model on a hardware simulator. It should be noted that for most hardware simulators, the operation of polling a facility within a simulation model during a simulation run is often a time consuming operation. In fact, if facilities must be polled every cycle, it is often the case that as much time, if not considerably more, is spent polling a simulation model for results rather than running the actual simulation. As such, it is advantageous when using a hardware simulator to avoid polling facilities within the model during a simulation run. In addition, many hardware simulators provide a facility that instructs the hardware simulator to run a simulation without interruption until a specific signal within the simulation model attains a specific value. This facility usually results in the highest performance for a simulation run on a hardware simulator.

In order to execute simulation model 520 on a hardware simulator, one or more instances of instrumentation entities, such as CHK1 550 a and CHKN 550 n, are instantiated in simulation executable model 520. As indicated, each instrumentation entity instantiation 550 generates from one or more input signals a set of external signals including an external phase signal 432 of one or more bits. At least one bit among external phase signals 432 can be defined as having an “end-of-testcase” (EOT) phasename and is employed to signal occurrence of EOT phase events. HDL compiler 462 also instantiates end-of-testcase combining logic 427 n (in this case, an AND gate 552) within the instrumentation logic block 420 of simulation model 520 to implement the combining function predefined for the EOT phasename for simulation model 520. The assertion of the output of such end-of-testcase combining logic 427 n, that is, termination signal 513 output by AND gate 552, thus indicates that the end of a testcase has been reached. Without termination signal 513, it would be necessary to directly poll facilities within simulation model 520 to determine when a simulation run is complete. Other phase events reported within external phase signals 432 are combined by combining logic 427 a-427 m to generate aggregate phase event signals 429 a-429 m within instrumentation logic block 420, as described above.

To efficiently locate and diagnose problems in simulation model 520, it is also advantageous to allow a simulation run to be stopped immediately whenever a failure event occurs during simulation of simulation model 520. (Harvest events and count events are typically only polled at the end of a simulation run.) Stopping simulation immediately upon occurrence of a failure event allows a user to easily locate the failure event within the simulation run, thereby facilitating debugging of the failure. If an EOT phasename is predefined for a simulation executable model 520, a logical OR gate 515 will automatically be included within the simulation model 520. Logical OR gate 515 receives as inputs termination signal 513 and the failure signal 511 generated by OR gate 512 and produces as an output the logical OR of signals 511 and 513 on signal 516. Signal 516 is therefore asserted to a logical ‘1’ whenever the simulation run has completed (signal 513 high) or a failure event has occurred (signal 511 high). In the alternative, if an EOT phasename is not predefined for simulation executable model 520, logical OR gate 515 is not included in the model and failure signal 511 is directly connected to signal 516. The name of signal 516 is fixed to a particular name by convention.

While the above described system and method provides a practical means of instrumenting simulation models, in certain circumstances additional techniques may be used in order to enhance the ease with which a user may instrument a simulation model. In design, it often occurs that there are common design or instrumentation logic constructs that are often repeated and possess a regular structure.

By utilizing knowledge of the regular structure of these design and instrumentation logic constructs, it is often possible to define a syntax that describes the instrumentation logic with considerably greater efficiency than would be possible utilizing a conventional HDL construct. By utilizing this syntax as an unconventional HDL comment within a design VHDL file, it is possible to create instrumentation entities with considerably greater ease and efficiency.

Such comments within a design entity will be referred to hereinbelow as an embedded instrumentation entity comment while the instrumentation logic created by such a comment will be referred to as an embedded instrumentation entity.

A common logic design construct is the so-called “finite state machine”. A finite state machine typically consists of a number of storage elements to maintain the “state” of the state machine and combinatorial logic that produces the next state of the state machine and its outputs. These constructs occur with great frequency in typical logic designs and it is advantageous to be able to efficiently instrument these constructs.

A typical set of count and failure events for a finite state machine includes counting the number of times a state machine cycles from a given current state to some next state, counting the number of functional cycles the state machine spends in each state, ensuring that the state machine does not enter an illegal state, and ensuring that the state machine does not proceed from a current given state to an illegal next state. This list of events is but one of many possible sets of events that can be used to characterize a finite state machine and is used in an illustrative manner only.

With reference now to FIG. 6 there is depicted a representation of an exemplary state machine 800. Exemplary state machine 800 consists of five states, labeled S0, S1, S2, S3, and S4 respectively, and nine legal state transitions between these states. In what follows, it is assumed that state machine 800 consists of three latches and a set of combinatorial logic to produce the next state function. It is further assumed that the states are encoded into the three latches following the usual and customary encoding for integers. That is to say, state S0 gets an encoding of 000_(bin), state S1 gets an encoding of 001_(bin), state S2 gets and encoding of 010_(bin), and so on.

With reference now to FIG. 7 there is shown an exemplary design entity 850 referred to as entity FSM with instance name FSM, which contains one instance of state machine 800. Furthermore, a signal output 801, “fsm_state (0 to 2)”, contains a three bit signal directly connected to the outputs of the three storage elements comprising the state elements of state machine 800. A signal input 802, fsm_clock, applies a clocking signal that controls the storage elements for state machine 800.

In order to instrument state machine 800, it would conventionally be necessary to create an instrumentation entity VHDL file containing the logic necessary to detect the desired state machine events and pass them through to count and fail events. Such an instrumentation entity file with appropriate instrumentation entity descriptor comments would typically require substantially more lines of code than the HDL description of the state machine itself. Such a circumstance is undesirable. However, in the case of a regular logic structure such as a finite state machine, it is possible to define a brief syntax that characterizes the finite state machine without resorting to a separate instrumentation VHDL entity.

With reference now to FIG. 8 there is illustrated an exemplary HDL file 860 for generating design entity 850 with an embedded instrumentation entity for monitoring the behavior of FSM 800. Specifically, an embedded instrumentation entity comment 852 is illustrated. As depicted in FIG. 8, embedded instrumentation entity comment 852 comprises a number of distinct sections including: a prologue and embedded instrumentation name declaration 853, a state machine clock declaration 859, a state element declaration 854, a state naming declaration 855, a state element encoding declaration 856, a state machine arc declaration 857, and an epilogue 858.

Prologue and embedded instrumentation entity name declaration comment 853 serves to declare a name that is associated with this embedded instrumentation entity. This comment line also serves to delineate the beginning of an embedded instrumentation entity comment sequence.

As further depicted in FIG. 8, declaration comment 853 assumes a non-conventional syntax of the form: “--!! Embedded TYPE: name”, wherein “--!! Embedded” serves to declare an embedded instrumentation entity, “TYPE” declares the type of the embedded instrumentation entity B FSM in this case, and “name” is the name associated with this embedded instrumentation entity.

State machine clock declaration comment 859 is utilized to define a signal that is the clocking control for the finite state machine.

State element declaration comment 854 is utilized to specify the state-machine state storage elements. This comment declares the storage elements or signal names that constitute the state-machine state. In state machine 800, the signals fsm_state (0 to 2) constitute the state machine state information.

State naming declaration comment 855 is utilized to declare labels to associate with various states of the given state machine. These labels are utilized in state machine arc declaration comment 857 when defining the legal state transitions within the given state machine.

State element encoding declaration comment 856 is utilized to define a correspondence between the state machine labels defined by state naming declaration comment 855 and the facilities declared by state element declaration comment 854. In the example shown, the labels of comment 855 are associated by position with the encodings given in comment 856 (i.e., the state labeled “S0” has the encoding 000_(bin), the state labeled “S1” has the encoding 001_(bin), etc.).

State-machine arc declaration comment 857 defines the legal state transitions within the state machine. The various transitions of the state machine are given by terms of the form “X=>Y” where X and Y are state machine state labels given by comment 855 and X represents a previous state machine state and Y a subsequent state machine state.

Epilogue comment 858 serves to close the embedded instrumentation entity comment. The specific syntax and nature of the comments between the prologue and embedded instrumentation name declaration and the epilogue will vary with the specific needs of the type of embedded instrumentation entity being declared.

Embedded instrumentation entity comment 852 is inserted within the VHDL file of the design entity that contains the finite state machine in question. The embedding of instrumentation for finite state machine 800 is made possible by the non-conventional comment syntax illustrated in FIG. 8 and is substantially more concise than a conventional HDL instrumentation entity suitable for accomplishing the same function.

Utilizing such embedded non-conventional comments, the system of the present invention creates an instrumentation entity, as described below, for instrumenting the state machine without the need to resort to creating a separate HDL file instrumentation entity.

To support compilation and creation of embedded instrumentation entities, the previously described compilation process of FIG. 4D is enhanced as described herein. First, HDL compiler 462 is altered to recognize the presence of embedded instrumentation entity comments. If, during compilation of a design HDL file, and subject to the constraints described above for incremental compilation, HDL compiler 462 detects one or more embedded instrumentation entity comments within the source code file, HDL compiler 462 places a special marker into design entity proto data structure 463.

When instrumentation load tool 464 is passed control, proto data structures 463 are searched in order to locate the special marker placed by HDL compiler 462 indicating embedded instrumentation entity comments. Such protos represent the design HDL files with embedded instrumentation entities that have been re-compiled in the current compilation cycle.

When instrumentation load tool 464 locates a proto data structure 463 with the special marker, the corresponding VHDL source code file for the design entity is opened and parsed to locate the one or more embedded instrumentation entity comments. For each of these comments, instrumentation load tool 464 creates a specially named proto data structure 463 a, and further generates a corresponding instance data structure 465 a that is instantiated within the design entity. In addition, instrumentation load tool 464 removes the special marker inserted by HDL compiler 462 to prevent unnecessary re-instrumentation of the design proto on subsequent re-compiles.

Within these created embedded instrumentation entity protos, instrumentation load tool 464 directly creates the necessary instrumentation logic required by the embedded instrumentation entity without the need for a VHDL file to specify this instrumentation and connects this logic to instrumentation logic block 420 of FIG. 4D. The updated design proto along with the embedded instrumentation entity proto and instance data structure are saved to disk and serve as inputs to subsequent compiles, removing the need to produce embedded instrumentation entities on subsequent recompiles.

With reference now to FIG. 9, design entity 850 is shown instrumented with embedded instrumentation entity 900. Embedded instrumentation entity 900 is created as a proto instantiated within design entity 850 wherein the embedded non-conventional instrumentation entity comment occurs. The embedded instrumentation entity thus may be replicated automatically within an overall design wherever the specific design entity is instantiated.

Embedded instrumentation entity 900 is named in a unique manner based on the name associated with the embedded instrumentation entity by the prologue and embedded instrumentation name declaration comment. This name is pre-pended with a special character (shown as a “$” in FIG. 9) that is not a recognized naming convention for the platform HDL. In this manner, the names of the embedded instrumentation entities cannot conflict with the names of any other design or standard instrumentation entities.

Furthermore, the names associated with the various events defined by the embedded instrumentation entity (the “varname” for the count events, for example) are also derived in a fixed manner from the name associated with the embedded instrumentation entity. The user is required to ensure that the names of embedded instrumentation entity events do not conflict with the names of standard instrumentation entity events and further than the names of the embedded instrumentation entities within a given design do not themselves conflict.

It should also be noted that if a design entity contains more than one embedded instrumentation entity, the embedding process described with reference to FIG. 8 and FIG. 9 is simply repeated for each such instrumentation entity. In addition, since the protos for the embedded instrumentation entities are created at the same time as the design protos itself, no changes to the BOM mechanism used for incremental compiles are required. The protos for the embedded instrumentation entities can be considered, for purposes of incremental compilations, to be mere extensions to the design proto itself.

The present invention discloses a method and system for naming events within a simulation model that prevents name collisions between events in different instrumentation entities, allows for the arbitrary re-use of components of a model in models of arbitrarily increasing size, and furthermore allows for processing designated events in a hierarchical or non-hierarchical manner.

When all instances of an event are considered as a whole without regard to specific instances, the event is considered in a “non-hierarchical” sense. Likewise, when an event is considered with regard to each and every instance, it is considered in a “hierarchical” sense. When considering count events, for example, it is often convenient to track the number of times a particular count event occurred in the aggregate without concern to exactly how many times the count event occurred in each particular instance within a simulation model.

Each type of event: count, fail, harvest and phase, is given a separate event namespace by construction. Each event class is therefore an independent group preventing naming collisions between the event types. The data structure of the present invention is independently applied to each of the different event types to ensure correctness within each event class.

In the embodiments illustrated in FIGS. 10A, 10B, 10C, and 10D, the system and method of the present invention are described with respect to count events. One skilled in the art will appreciate and understand the extensions necessary to apply the same techniques to other event classes such as failures, harvests and phases.

With reference to FIG. 10A, there is depicted a block diagram representation of simulation model 1000 containing a number of design and instrumentation entities. As illustrated in FIG. 10A, simulation model 1000 includes two instances of a design entity X, with instance names X1 and X2 respectively. Within each of design entity instances X1 and X2 is instantiated an instance of an instrumentation entity B3, 1012 a and 1012 b. Design entity instances X1 and X2 further comprise instances, 1014 a and 1014 b, respectively, of design entity Z which further contains instances, 1016 a and 1016 b, of instrumentation entity B1 and instances, 1018 a and 1018 b, of instrumentation entity B2.

Finally, simulation model 1000 includes an instance of design entity Y, with instance name Y, containing an instance of instrumentation entity B4 1022. Design entity instance Y contains an instance, 1024, of design entity Z with further instances, 1016 c and 1018 c, of instrumentation entities B1 and B2 respectively.

In what follows the methods of the present invention for uniquely naming events will be considered in the context of exemplary model 1000. It will be assumed in the following description that each instrumentation entity (B1, B2, B3, and B4) has declared a single count event with event name “count1”.

In accordance with the method and system of the present invention, the user must uniquely name each type of event (count, fail, harvest or phase) within a specific instrumentation entity, i.e., the user cannot declare any two events of the same type within the same instrumentation entity with the same event name. Such a constraint does not conflict with the stated goals of the present invention in that a given instrumentation entity is usually created by a specific person at a specific point in time, and maintaining unique names within such a limited circumstance presents only a moderate burden to the user. The data structure disclosed herein does, however, prevent all name collisions between events in different instrumentation entities, and allows for processing the events in a hierarchical and/or non-hierarchical manner.

As previously explained, an HDL naming convention must uniquely identify all the entities within a given design. This constraint is inherent to HDLs and applies to design entities as well as instrumentation entities. In accordance with conventional VHDL entity naming constructs, it is technically possible for two design entities to share the same entity name, entity_name. However, such identically named entities must be encapsulated within a VHDL library from which a valid VHDL model may be constructed. In such a circumstance, entity_name, as it is utilized herein, is equivalent to the VHDL library name concatenated by a period (“.”) to the entity name as declared in the entity declaration.

Pre-pending a distinct VHDL library name to the entity name disambiguates entities sharing the same entity name. Most HDLs include a mechanism such as this for uniquely naming each design entity. Design entities must be unambiguously named in order to determine which particular entity is called for in any given instance in a simulation model. The present invention employs the prevailing naming mechanism of the native HDL to assign unique entity names for design entities throughout a given model and leverages the uniqueness property of entity names and the uniqueness of each instance's instantiation identifier to create an “extended event identifier” for each event within the simulation model.

With reference to FIG. 10B, there is illustrated a representation of the fields in an extended event identifier data structure, alternatively referred to herein as an “event list”, in accordance with one embodiment of the present invention. The extended event identifier begins with instantiation identifier field 1030. This field, as described hereinbefore, consists of the instance identifiers, proceeding from the top level entity to the direct ancestor of the given instance within the simulation model separated by periods (“.”). This string is unique for each and every instance of the event within the model. The extended event identifier further includes an instrumentation entity field 1032, a design entity field 1034, and an eventname field 1036.

Instrumentation entity field 1032 contains the name of the instrumentation entity (or the name assigned to an embedded instrumentation entity) that generates the simulation event. Design entity field 1034 contains the entity name of the design entity in which the event occurs. Eventname field 1036 is the name given to the event in the instrumentation entity description comments of an instrumentation entity or the event name assigned to an event within an embedded instrumentation entity. These four namespace fields comprise a unique identifier for each event within a simulation model that allows for the re-use of components within other models without risk of name collisions and the consideration of events in a hierarchical or non-hierarchical sense.

With reference now to FIG. 10C, there is shown a list of extended event identifiers for model 1000. Event identifiers 1040, 1041, 1042, 1043, 1044, 1045, 1046, 1047, and 1048 are declared within simulation model 1000 to designate count events having eventname “count1”. The extended event identification procedure of the present invention will be described in the context of these extended event identifiers.

The uniqueness of the names in design entity name field 1034 is a primary distinguishing factor between events. By including the design entity name in the extended event identifier, each design entity is, in effect, given a unique namespace for the events associated with that design entity, i.e., events within a given design entity cannot have name collisions with events associated with other design entities.

It is still possible however, to have name collisions between events defined by different instrumentation entities that are incorporated within a single design entity. Events 1041 and 1042, for example, if identified solely by the design entity name, have a name collision. Both are events with eventname “count1” within design entity Z, and if labeled as such, are indistinguishable. In order to alleviate a naming collision between events 1041 and 1042, the present invention employs instrumentation entity field 1032. By referencing the design entity and instrumentation entity names, both of which are unique with respect to themselves and each other, a unique event namespace is created for each instrumentation entity associated with any given design entity. For example, event identifier 1041 and 1042 would be in conflict (both named Z.count1), unless the respective instrumentation entity names are included within the extended event identifier to produce names B1.Z.count1 and B2.Z.count2 for these events.

It should be noted that it is possible to uniquely name each event by using instrumentation entity name field 1032 alone. Due to the uniqueness property of instrumentation entity names, event names that are only named by the instrumentation entity name and the event name field will be necessarily unique.

However, such a naming scheme is insufficient for associating events with a given design entity. In practice, it is desirable to associate events with the design entity in which they occur rather than associating them with the potentially numerous instrumentation entities that are utilized to track them. Moreover, referencing the appropriate design entity within the eventname allows all the events associated with a given design entity to be centrally referenced without the need to ascertain the names of all the instrumentation entities associated with the given design entity. The data structure of the present invention utilizes both the instrumentation entity and design entity names in naming events for ease of reference at the cost of moderate uniqueness redundancy in the event names.

In an alternative embodiment of the present invention, the instrumentation entity name is not included within the extended event identifier. Referring to FIG. 10D, such an alternative extended event identification data structure is depicted. As shown in FIG. 10D, events are named by instantiation identifier field 1030, design entity name field 1034, and event name field 1036.

Such a data structure provides name collision protection between design entities but not within design entities. That is, the user must ensure that events names for events associated with a given design entity do not collide. In case of user error in this regard, model build tools may be utilized to detect an event name collision condition during model compilation. The alternative data structure depicted in FIG. 10D provides for simpler naming and referencing of events at the expense of requiring the user to prevent name collisions for events associated with a given design entity.

Returning to FIG. 10B, the combination of instrumentation entity field 1032, design entity name field 1034, and eventname field 1036 for a given event, provides a unique identifier for any given event without regard to multiple instantiations of the event. In order to uniquely distinguish between multiple instantiations of an event, instantiation identifier field 1030 is included in the extended event identifier. Instantiation identifier field 1030 field, by its construction, provides a unique string for any instance of an entity within any simulation model.

When evaluating occurrences of an event in a non-hierarchical sense, instantiation identifier field 1030 is ignored while searching for matching events. As illustrated in FIG. 10C, for example, a non-hierarchical query for the number of time a “count1” event occurs within design entity Z as detected by instrumentation entity B1, utilizes the following list of count eventnames:

X1.Z B1 Z COUNT1 X2.Z B1 Z COUNT1 Y.Z B1 Z COUNT1.

These count events are added together to form an aggregate count of the total number of time the specific event occurred within the simulation model.

A hierarchical query includes specific criteria to match against the hierarchy field to limit the counter or counters found to specific instances of the requested event. For example, a query to obtain the count1 event of instrumentation entity B1 within the X1.Z instance of design entity Z utilizes the following count eventname:

X1.Z B1 Z COUNT1, which represents the number of times the count1 event was counted by instrumentation entity B1 within design entity instance X1.Z for a particular simulation interval.

By providing matching model hierarchy criteria against instantiation identifier field 1030, it is possible to consider the events with respect to their particular instance or instances within the model, i.e., a hierarchical query. A non-hierarchical query merely ignores the hierarchy field and returns all the instances of the requested events within the model.

With reference to FIG. 11A, there is depicted a block diagram illustrating a simulation model 1100 in which the hierarchical event processing of the present invention is applicable. Simulation model 1100 comprises a top-level design entity 1130 in which a pair of lower-level design entities 1102 and 1120 is instantiated. A design entity 1104 containing instrumentation entity 1106 is included within design entity 1102. As illustrated in FIG. 11A, instrumentation entity 1106 includes logic 1110 for generating a simulation event 1108 from signal set 1132 from within design entity 1104. Design entity 1120 includes an instrumentation entity 1122 that generates a simulation event 1124 using signal set 1134.

Utilizing the techniques described hereinbefore, generating a hierarchical event that is some logical combination of events 1108 and 1124 requires the creation of an instrumentation entity associated with top level design entity 1130 that references signal sets 1132 and 1134. Conventionally, such an instrumentation entity would substantially reproduce instrumentation logic 1110 and 1126 to process signal sets 1132 and 1134, respectively, thus producing a copy of events 1108 and 1124. Such a procedure is inefficient and prone to error. If, for example, changes are made to any or all of signal sets 1132 and 1134, or instrumentation logic 1110 and 1126, these changes would have to be accurately repeated in the instrumentation entity logic for the combined event.

The present invention provides a mechanism whereby events, such as events 1108 and 1124, are directly referenced and utilized as inputs to cross-hierarchical instrumentation entities. In this manner, signal connections 1132 and 1134, as well as instrumentation logic 1110 and 1126, are directly re-utilized to produce the desired hierarchical event.

To facilitate direct referencing of events within simulation models, a specialized data structure is implemented within instrumentation entity input port map comment syntax. This data structure directly connects input ports of instrumentation entities to cross-hierarchical events within a simulation model.

For the embodiment depicted in FIG. 11A, an instrumentation entity 1150 is instantiated within top-level design entity 1130 to generate a hierarchical event 1156 that is some function of events 1108 and 1124. As illustrated in FIG. 11A, instrumentation entity 1150 includes a pair of inputs 1151 and 1152 that are directly connected to events 1124 and 1108, respectively, utilizing the augmented syntax described below. These input connections are logically combined using instrumentation logic 1154 to produce a cross-hierarchical event 1156.

With reference to FIG. 11B, there is depicted a set of input port mapping comments for performing cross-hierarchical processing of simulation model events in accordance with the teachings of the present invention. In what follows, it is assumed that events 1108 and 1124 are count events with event names event_1108 and event_1124, respectively, and that these events are connected to input ports event_1108_in and event_1124_in on instrumentation entity 1150. As depicted in FIG. 11B, a first input port mapping comment 1161 contains data for referencing event 1108 to input port event_1108_in. A second input port mapping comment 1162 contains data for referencing event 1124 to input port event_1124_in. It should be noted that each of input port mapping comments 1161 and 1162 includes a pre-pended non-conventional comment identifier,--!!, that is utilized by the HDL compiler (such as compiler 462 in FIG. 4D) to maintain the port mapping comments separate from the design.

To facilitate connection of a simulation event to an instrumentation entity input port, input port mapping comments 1161 and 1162 consist of two distinct parts: an instance identifier and an event identifier. The instance identifier is a string consisting of instance names (in descending hierarchical order) of all design entities between and including the design entity containing the instrumentation entity of the cross-hierarchical event being defined (i.e., the highest level design entity for the cross-hierarchical event), and the design entity in which the event that is utilized in generating the cross-hierarchical event. If the design entity containing the hierarchical event is the same as the design entity containing the event to be connected to, the instance identifier is a null string. A pair of instance identifiers 1163 and 1164 within input port mapping comments 1161 and 1162, respectively, specify that events 1124 and 1108 originate from signals within design entity 1120 and 1104, respectively.

Input port mapping comments 1161 and 1162 further include event identifiers 1165 and 1166 that identify input simulation events in terms of local instrumentation entities 1106 and 1122, respectively. In accordance with the embodiment depicted in FIG. 11B, each event identifier consists of a string beginning with an open bracket (“[”) character and ending with a closed bracket (“]”) character. Between these brackets, three sub-strings, delineated by period (“.”) characters, comprise a data structure utilized to identify a specific event from which the cross-hierarchical event is defined. The first sub-string within an event identifier is the instance name of the instrumentation entity containing the event. The second sub-string is a string specifying the type of the event (“count”, “fail”, “harvest”, or “phase”). Finally, the third sub-string is the event name of the given event as specified in the declaration comment for the event. Each event identifier string uniquely identifies a single event within a given design entity. As depicted in FIG. 11B, event identifier strings 1165 and 1166 identify events 1108 and 1124 respectively.

In accordance with an alternate embodiment of the present invention, the event identifier naming structure is modified slightly for events that are labeled in accordance with FIG. 10D (event names that do not include the instrumentation entity name). When an instrumentation identifier is absent from the extended event identifier, the event identifier string with an input port mapping comment consists of two sub-strings: a string denoting the type of event to connect to; and a string providing the name of the event separated by a period (“.”) character. The instrumentation entity name is not required in this case since all events of a given type associated with a given design entity will have unique names. The model build tools of the present invention will automatically search all instrumentation entities associated with the design entity called out by the instance identifier to determine which instrumentation entity generates an event having the name and type provided in the event identifier string.

Referring to FIG. 11C, there is illustrated a set of data structures for performing hierarchical processing of simulation model events in accordance with a second embodiment of the present invention. In the depicted embodiment, a pair of input port mapping comments 1171 and 1172 employs syntax compatible with the event naming data structure depicted in FIG. 10D.

Input port mapping comment 1171 connects event 1108 to input port event_1108_in on instrumentation entity 1150. Likewise, input port mapping comment 1172 connects event 1124 to input port event_1124_in on instrumentation entity 1150. By utilizing the augmented syntax of FIG. 11B or FIG. 11C, it is possible to create hierarchical events by connecting the inputs of instrumentation entities to events within the simulation model.

The above described system and method provides for practical instrumentation of simulation models and allows for efficient implementation of instrumentation logic through embedded instrumentation entities. Embedded instrumentation entities, as described hereinabove, are however necessarily limited to task-specific implementations. As described with reference to FIGS. 12A and 12B, the present invention further provides for a more flexible implementation of instrumentation logic in a more unstructured manner.

It is often necessary to tailor instrumentation logic to address unique problems and circumstances. Instrumentation logic of a specific and yet non-predefined nature that is designed in accordance with the techniques disclosed herein with reference to FIGS. 12A and 12B is referred herein as “random instrumentation logic.” A data construct consisting of general logic primitives (Boolean operators, storage elements, etc.) and an interconnection method for these primitives is utilized for implementing such random instrumentation logic.

For instrumenting a simulation model as described heretofore, an HDL such as VHDL or Verilog is utilized as a platform from which instrumentation logic is generated. Appropriate instrumentation entity descriptor comments within design entity source code files couple the resultant instrumentation entities to designated target design entities within a simulation model.

In addition to entity descriptor comments within a design entity source code file, the foregoing instrumentation technique requires a separate HDL file in which the instrumentation entity is described. As explained with reference to FIGS. 12A and 12B, the present invention provides a method, system, and data structure for instrumenting design entities within a simulation model while avoiding the design process overhead required for creating a separate instrumentation entity HDL file.

In accordance with the teachings of the present invention, random instrumentation logic is directly deployed within target design entities in terms of individualized and customizable instrumentation descriptor comments. Such instrumentation descriptor comments are encoded within the target design entity HDL source code file and provide a means for the describing random instrumentation logic, events, and interconnections between the created instrumentation logic and the target design entity. The random instrumentation logic is inserted into the simulation model in a manner similar to the techniques used for embedded instrumentation entities to produce an instrumentation entity without the need for the creation of an explicit HDL instrumentation entity file.

With reference to FIG. 12A, there is illustrated a representative target design entity 1200 wherein random instrumentation logic is implemented in accordance with a preferred embodiment of the present invention. Instantiated within target design entity 1200 is a design entity 1201. As further depicted in FIG. 12A, an instrumentation entity 1202 is instantiated within design entity 1201. Instrumentation entity 1202 is designed in accordance with the principles set forth hereinabove to generate a count event 1203 having an event name “count1.” Target design entity 1200 further includes an instrumentation entity 1208 that is generated utilizing random instrumentation logic. As depicted in FIG. 12A, instrumentation entity 1208 receives as inputs signals P, R, A, B, C and D along with count event 1203.

Instrumentation entity 1208 is constructed by a set of unconventional comments lines within the source code file for target design entity 1200. These comments may be incorporated at any point within the logic description section of the HDL source code file. HDL compiler 462 (FIG. 4B) recognizes the unconventional comments in addition to any comments utilized to instantiate embedded instrumentation entities within design entity 1200. During the post-compilation/model build phase, instrumentation load tool 464 processes these comments in a manner similar to that utilized for embedded instrumentation entities (described with reference to FIGS. 10A-10D) to generate instrumentation entity 1208.

A variety of possible syntaxes can be utilized to formulate the unconventional HDL comments required for generating random instrumentation logic within the source code file of a target design entity. As depicted in FIG. 12B, much of the syntax of these comments employs syntax similar to the concurrent subset of the VHDL language with the addition of syntactic and semantic enhancements that provide a means of connection between an instrumentation entity and its target design entity. In addition, minor syntactic and semantic enhancements are provided to declare events and intermediate signals.

With reference now to FIG. 12B, there is illustrated an exemplary HDL source code file 1220 that describes design entity 1200 of FIG. 12A. Within HDL source code file 1220, an entity instantiation 1221 produces design entity 1201, and assignment statements 1222 are utilized to generate signals A, B, C and D. A set of unconventional comments 1223 within HDL source code file 1220 is utilized to produce instrumentation entity 1208. Comments 1223 are formulated as left-hand side (l.h.s.)/right-hand side (r.h.s.) assignment statements of the form: {l.h.s.}<={r.h.s}; where {l.h.s.}, referred to hereinafter as lhs, is the assignment statement target and, {r.h.s}, referred to hereinafter as rhs is an expression denoting the logical value to be assigned to the statement lhs. A number of rules delineate the possible expressions for lhs and rhs in any legal statement in the instrumentation comments.

As employed within the instrumentation data structure of the present invention, an lhs statement may be either an event declaration or the name of a signal that is instantiated within an instrumentation entity. An event declaration is an expression within bracket characters (“[A, A]”) that generates a new event. Within comments 1223, a statement 1230 produces a count event 1240 from instrumentation entity 1208 (FIG. 12A) having eventname “countname0”.

Within an lhs event declaration, a first field designates the event type (count, fail, harvest, phase, etc.) and is followed by such other fields as are necessary to declare the event. As illustrated in lines 1230, 1234, and 1236, such event declaration fields follow the same format as the event declaration fields depicted in FIG. 4C.

Comments 1223 further include a line 1232 having an lhs that declares a signal

 within instrumentation entity 1208. To prevent ambiguity, any signal declared in this manner may not have a name corresponding to the name of any signal present on the top level of target design entity 1200. Conformance to this requirement is verified by instrumentation load tool 464 (FIG. 4D) during processing. Signals declared by an lhs expression may be incorporated within an rhs expression as shown in lines 1232 and 1234.

An rhs consists of logical connectivity expressions and/or functions that combine various signals. Signals within these connectivity expressions may originate from a number of possible sources including: signals declared on the lhs of a statement in the instrumentation comments; signals within the target design entity; or signals designating other events within the target design entity.

The absence of period (“.”) or bracket (“[”, “]”) characters within a signal value description in the rhs of a statement, designates the object signal as corresponding to either a signal within the top hierarchical level of the target design entity or to a signal declared on the lhs of a statement within the instrumentation language. Signals are named in a mutually exclusive manner by the rules governing creation of signals on the lhs of a statement in the instrumentation comments, thereby preventing any ambiguity in the determining the source of the given signal.

Signals in rhs connectivity expressions can also be connections to signals within entities instantiated within the target design entity. In such a circumstance, the instance names of the entity or entities in the hierarchy enclosing the desired signal are placed before the signal name in hierarchy order, delineated by period (“.”) characters. For example, the signal in statement 1230 (“Y.P”) represents signal 1204 within design entity 1201. Signals at any level of the target design hierarchy are thus accessible to instrumentation logic generated by the instrumentation language comments.

Signals within the instrumentation comment expressions can also designate other events within the target entity. Event identifiers as described hereinbefore for hierarchical events are used to denote such “event” signals. For example, statement 1232 performs a logical AND of instrumentation event 1203 and signal A. The event identifier “Y.[B1.count.count1]” connects instrumentation entity 1208 to instrumentation event 1203. This notation permits instrumentation events at any level of design hierarchy within target design entity 1200 to be directly accessed.

As further depicted in FIG. 12B, statement 1232 produces intermediate signal

 within instrumentation entity 1208. This is an example of an instrumentation comment statement declaring a new intermediate signal. These signals can be used in other statements to construct random instrumentation logic of any desired depth or complexity.

Statement 1234 utilizes intermediate signal

 along with signal 1206 to produce fail event 1241. The syntax for fail event declaration includes a field denoting the type of event (“fail”), a field giving the event name for the fail event (“failname0”), and a final field denoting the message to associate with the fail. Statement 1236 produces harvest event 1242 by including within random instrumentation logic 1208 an AND gate that performs the specified logical operation B AND C. Finally, statement 1238 produces phase event signal 1250. In the case of phase event declaration, the lhs assignment expression target is of the form: [<eventtype>, <eventname>,<phasename>], where <eventtype> is “phase”, <eventname> is the name of the phase event, and <phasename> is the aggregate phase name. As described above, the external phase event signal 1250 generated by instrumentation entity 1208 will be combined with other phase events sharing the same aggregate phasename by an instance of combining logic 427. The instance of combining logic 427 implements the combining function specified for the aggregate phasename in phase file 492 (or predefined for the phasename) in order to generate the aggregate phase event signal 429 for the aggregate phasename (in this case end-of-testcase).

In general, the rhs expression of any statement in the instrumentation data structure of the present invention can access any signal or instrumentation event signal within the target design entity utilizing these syntactic mechanisms. These signals can be combined to form new events or intermediate signals that can themselves be further combined to form instrumentation logic of any desired depth or complexity.

Instrumentation comments can be placed anywhere within the logic description section of the target entity source code file. All instrumentation comments within a file are considered as a whole and produce a single instrumentation entity within the target design entity.

Simulation of a given model is typically controlled by a program, hereinafter referred to as RTX (Run Time eXecutive), that is written in a high-level language such as C or C++. To facilitate RTX control and execution of a simulation run, simulators typically provide a number of application program interface (API) functions that may be called by the RTX. Such API functions employ routines, protocols, and tools that allow for polling of signals within the simulation model, alteration of signals within a simulation model, cycling a simulation model, etc.

The RTX is often required to monitor occurrences of significant events during model simulation. Such events typically consist of a signal or a set of signals that assume a prescribed sequence of values and will be referred to hereinafter as “model events.” To monitor model signals, an RTX typically calls a specialized API function, hereinafter referred to as GETFAC, which allows for polling of signal values during model simulation.

Typically, an RTX must monitor a large number of signals, potentially on a cycle-by-cycle basis, within a simulation model and must subsequently process the signal values in order to detect the occurrence of model events. This approach to model event monitoring places a burden on the verification engineer in terms of re-writing RTX and communicating with design engineers when the signals or sequence of signal values that constitute a model event change.

To provide an efficient means for monitoring model events, so-called “detection events” are generated and are accessible by the RTX. Such detection events are generated by instrumentation entities. Detection events are implemented as output ports on an instrumentation entity. Furthermore, an enhanced API function is provided for directly accessing detection events within a given simulation model.

For each detection event, a first, potentially multi-bit, output is utilized as the value of a model event. An optional second single bit signal is utilized to indicate when the detection event occurs during model simulation. By their nature, certain model events occur at each and every cycle and therefore do not require a qualifying signal to track their occurrences.

With reference to FIG. 13A, there is illustrated a block diagram depicting data content within main memory 44 (FIG. 2) during a simulation run of a simulation model 1400. Main memory 44 includes the elements necessary for monitoring an exemplary model event including a software simulator 1410 that simulates simulation model 1400 under the control of an RTX 1405.

RTX 1405 delivers a set of API calls 1430 to API function GETFAC within simulator 1410 to obtain the values of signals A, B, C, and D within model 1400. Further processing of these signal events is performed utilizing an RTX code 1450 culminating in the assignment of the model event value to variable event_x at RTX code line 1455.

Referring to FIG. 13B, there is illustrated a block diagram depicting contents of main memory 44 during a simulation run in accordance with a preferred embodiment of the present invention. In the depicted embodiment, an instrumentation entity 1460 is instantiated within simulation model 1400 using techniques described above. Instrumentation entity 1460 directly monitors signals A, B, C, and D by means of a set of signal connections 1462. Signal connections 1462 provide a more efficient means to monitor signals than GETFAC API function calls.

Within instrumentation entity 1460, instrumentation logic 1464 substantially recreates the function of RTX code 1450 of FIG. 13A and produces signals 1466 and 1468, which denote the value of a model event (e.g., a fail, count, harvest or phase event) and when the model event occurs, respectively.

Each detection event within a given simulation model is assigned a unique name in a manner described below. During model build, instrumentation load tool 464 (FIG. 4D) generates a data structure in the form of a table within the simulation model that uniquely names all the detection events within a given simulation model and the corresponding instrumentation entity output signals. This table will be referred to hereinafter as the detection event translation table.

An API function GETEVENT( ) is provided within software simulator 1410 for accessing model detection events. API function GETEVENT references a detection event translation table 1470 to locate signals 1466 and 1468 in response to a call 1472 by RTX to obtain the value of model event event_x. RTX 1405 obtains the value of model event event_x without delivering a number of GETFAC API calls, and furthermore, without the need to process the signal values associated with the model event. The RTX code is thus insulated from potential changes to the signals and signal sequence values defining model event event_x. Any changes to the detailed definition of model event event_x are reflected within instrumentation entity 1460 and no changes to the RTX are necessary.

It will further be appreciated that one or more variants of the API function GETEVENT( ) may be defined to support different parameter sets for different types of events. For example, a first API function GETPHASE (phasename, instance) can be defined to obtain the logic value of the specified phase event, as optionally further qualified by an instance parameter identifying a particular target design entity instance within the simulation model. A second API function GET_AGG_PHASE (phasename) can further be defined to obtain the logic value of the aggregate phase event signal 429 for the specified aggregate phasename.

With reference to FIG. 13C, there is illustrated an exemplary HDL source code file 1480 that describes instrumentation entity 1460 in accordance with a preferred embodiment of the present invention. As shown in FIG. 13C, exemplary file 1480 consists of a number of entity descriptor comments 1491 and an architecture section 1492 comprising instrumentation logic 1464.

Within HDL file 1480, a set of input port map comments 1493 serve to generate connections 1462 of FIG. 13B. An additional comment section, detection declarations 1494 is incorporated within the entity descriptor comment syntax that allows for declaring detection events. A detection declaration comment 1495 serves to generate and uniquely name detection event event_x. Moreover, detection declaration comment 1495 associates signals 1466 and 1468 of FIG. 13B with event_x. Detection event declarations, such as detection event declaration 1495 are of the form: --!!<name>: event_value_port [ctrl_signal]; where name is a name associated with the specific detection event (event_x in FIG. 13C), event_value_port is the output port providing the value for the detection event, and ctrl_signal is an optional single bit output port that flags an occurrence of the model event.

Each detection event is uniquely named in accordance with the name field within the output declaration comment in a manner analogous to that described earlier for count events. Such detection event names, together with the corresponding instrumentation entity output ports, are inserted into the detection event translation table data structure that is placed within the model by instrumentation load tool 464. API function GETEVENT receives the extended event identifier associated with a given event as an input and returns the model event value and, if applicable, an indication of whether the event occurred in the current cycle.

While FIG. 13C illustrates only those constructs necessary for implementing a detection event, the principles set forth herein place no limitation on the generation of count, fail, harvest or phase events or signal overrides within the same instrumentation entity as a detection event. Moreover, multiple detection events may be incorporated within the same instrumentation entity.

Within the spirit and scope of the present invention, detection events may be created within random instrumentation comments in a manner largely similar to that described with reference to signal overrides. Detection events can also be combined, in a manner similar to that shown earlier, as part of a hierarchical event.

Finally, it should be noted that the present invention may be practiced in conjunction with a hardware simulator. As for software simulators, hardware simulators are controlled by an RTX program. To adapt the principles set forth herein to a hardware simulator environment, the hardware simulator provides a GETEVENT API function and accepts models containing a detection event translation table.

By utilizing random instrumentation comments, a design engineer can efficiently create representations of model events accessible to RTX. Such representations need not change even if the detailed definition of the model event changes. Such stability reduces the complexity and burden of maintaining RTX and lowers the amount of communication required between design and verification engineers.

In order to provide for the control and monitoring of instrumentation events within simulation models executing on a batch simulation farm, one or more general-purpose computers, hereinafter referred to as “instrumentation servers”, are added to batch simulation farms. An instrumentation server acts as a centralized repository for information used to control instrumentation events and for data gathered from instrumentation events during simulation runs. The exact nature and function of the control information and of the gathered data varies with the type of event (i.e., fail events vs. count events), as will be described below.

In order to allow for effective management of instrumentation events, a set of “eventlist” files (described with reference to FIGS. 10A-10D) contain information about the exact number and content of the instrumentation events in a given model. The eventlist files are created at model build time by instrumentation load tool 464. These files, one per class of events (fail, count, harvest, phase etc.), list the particular events in the given simulation model. Each simulation model has a unique set of corresponding eventlist files that are created at model build time.

When instrumentation events are created at model build time, they are constructed in a specific order, and a unique index is assigned within the eventlist file to each instrumentation event for a given event class. Accesses to instrumentation events by API routines make use of these index values. Furthermore, when an API routine communicates aggregate data with respect to all events within a given event class to the instrumentation server, this aggregate data is sequentially ordered according to these index values.

Each eventlist file contains a list of the instrumentation events for a given event class within the model. These events are named in accordance with the naming convention data structures described above in conjunction with FIGS. 10A-10C, which provides unique names for each of the instrumentation events. Referring back to FIG. 10A in conjunction with FIG. 14, there is shown an eventlist file 1660 for the count events of simulation model 1000 of FIG. 10A.

Eventlist file 1660 contains multiple count event class entries 1663. Each of count event class entries 1663 includes a unique, sequential index value 1661, and an extended event identifier 1662. Each of indices 1661 corresponds to the index of a particular event (in this case count event COUNT1) assigned at model build time. Extended event identifiers 1662 provide an event name associated with each individual event index. Eventlist file 1660 thus provides a mapping between the instrumentation event names and the instrumentation event indices as well as providing an ordering convention for aggregate data for a class of instrumentation events. Eventlist files, such as eventlist file 1660, are used by the instrumentation server to aid in the control and monitoring of instrumentation events in simulation models.

As has been described, the present invention provides a method, system and program product for simulation processing. According to one embodiment of the invention, an instrumented simulation executable model of a design is built by compiling one or more hardware description language (HDL) files specifying one or more design entities within the design and one or more instrumentation entities and instantiating instances of the one or more instrumentation entities within instances of the one or more design entities. Operation of the design is then simulated utilizing the instrumented simulation executable model. In the simulation, each of multiple instantiations of the one or more instrumentation entities generates a respective external phase signal representing an occurrence of a particular phase of operation, and instrumentation combining logic generates from external phase signals of the multiple instantiations of the one or more instrumentation entities an aggregate phase signal representing an occurrence of the particular phase of operation, such as an end-of-testcase.

While the invention has been particularly shown as described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. For example, one of the embodiments of the invention can be implemented as sets of program code resident in random access memory 28 of one or more computer systems configured generally as described in FIG. 1 and FIG. 2. Until required by computer system 10, the set of program code may be stored in another computer readable storage device, such as disk drive 33 or in a removable storage device such as an optical disk for eventual use in a CD-ROM drive or a floppy disk for eventual use in a floppy disk drive. The set of program code embodied in a computer usable medium may be referred to as a computer program product. Further, the set of program code can be stored in the memory of another computer and transmitted over a local area network or a wide area network, such as the Internet, when desired by the user. 

1. A method of simulation processing in a data processing system, said method comprising: building an instrumented simulation executable model of a design, said building including compiling one or more hardware description language (HDL) files specifying one or more design entities within the design and one or more instrumentation entities and instantiating instances of the one or more instrumentation entities within instances of the one or more design entities, wherein said step of instantiating comprises instantiating each of the instances within a particular design entity indicated by the one or more HDL files, and wherein said instrumented simulation executable model includes a plurality of instances of said one or more design entities; simulating operation of the design utilizing the instrumented simulation executable model, wherein said simulating includes: each of multiple instantiations of the one or more instrumentation entities generating from one or more signals in at least one instance of the one or more design entities a respective external phase signal representing an occurrence of a particular phase of operation, wherein said particular phase is an end-of-testcase phase indicating that an end of a simulation testcase has been reached; identifying each of a plurality of phases of operation of said instrumented simulation executable model with a respective phasename; restricting application of at least one phasename to a region of the instrumented simulation executable model defined by one of said plurality of instances of said one or more design entities; instrumentation combining logic generating from external phase signals of the multiple instantiations of the one or more instrumentation entities an aggregate phase signal representing an occurrence of the particular phase; and the data processing system automatically halting simulation of the design in response to the aggregate phase signal indicating an occurrence of the end-of-testcase phase.
 2. A program product, comprising: a computer-readable storage medium; and model build program code within the computer-readable storage medium that, when processed by a data processing system, builds an instrumented simulation executable model of a design by performing a model build process including: compiling one or more hardware description language (HDL) files specifying one or more design entities within a design and one or more instrumentation entities for instrumenting the design entities for simulation; generating instrumentation combining logic that aggregates external phase signals of instances of the one or more instrumentation entities; and integrating instances of the one or more instrumentation entities and the instrumentation combining logic into instances of the one or more design entities to obtain the instrumented simulation executable model of the design, wherein in the instrumented simulation executable model, multiple instantiations of the one or more instrumentation entities are each coupled to receive as inputs one or more signals in instances of the one or more design entities and to produce as an output a respective external phase signal representing an occurrence of a particular phase of operation, and wherein said instrumentation combining logic is coupled to receive as inputs the external phase signals and produce as an output an aggregate phase signal representing an occurrence of the particular phase; wherein: said model build program code instantiates the instantiations of the one or more instrumentation entities in instances of one or more design entities indicated by the one or more HDL files; said particular phase is an end-of-testcase phase indicating that an end of a simulation testcase has been reached. said instrumented simulation executable model includes a plurality of instances of said one or more design entities; and said model build program code identifies each of a plurality of phases of operation of said instrumented simulation executable model with a respective phasename and restricts application of at least one phasename to a region of the instrumented simulation executable model defined by one of said plurality of instances of said one or more design entities.
 3. A program product, comprising: a computer-readable storage medium; and an instrumented simulation executable model of a design within the computer-readable storage medium, said instrumented simulation executable model including: instances of one or more design entities defining the design, instantiations of one or more instrumentation entities that detect occurrences of specified event within the instances of the one or more design entities, and instrumentation combining logic, wherein multiple instantiations of the one or more instrumentation entities are each coupled to receive as inputs one or more signals in instances of the one or more design entities and to produce as an output a respective external phase signal representing an occurrence of a particular phase of operation, and wherein said instrumentation combining logic is coupled to receive as inputs the external phase signals and produce as an output an aggregate phase signal representing an occurrence of the particular phase, wherein: when simulated by a software simulator, said instrumented simulation executable model records the occurrence of the particular phase; said particular phase is an end-of-testcase phase indicating that an end of a simulation testcase has been reached; the instrumented simulation executable model automatically signals to halt simulation of the design in response to the aggregate phase signal indicating an occurrence of the end-of-testcase phase; and said instrumented simulation executable model reports said occurrence of the particular phase in response to a call querying for information regarding the particular phase. 